Once you have signed in, you will be ready to post on the blog. I am hoping that when you are in the blog, that in the upper right hand side, there is a heading that should say "new post". If it isn't there, on the far left side next to the search option, there is the orange symbol. You can try clicking on that symbol. That sends you to the "Dashboard" which has the option for "new post".
If "new post" and "dashboard" aren't available, you will need to "sign in" again. Go to the top left hand corner of the blog and hit the orange symbol. Then sign in using, I think, your address and password. At that point you should be able to post by following the above directions.
Hopefully, this will go smoothly for each of you. Do let me know if you are having problems. Again, have fun.